This document relates to RF and microwave devices based on photonic elements.
RF and microwave signal generation and processing may be achieved in the optical domain using photonic elements. Examples include generation of RF and microwave oscillations using opto-electronic oscillators and filtering of RF and microwave signals using optical filtering by narrow band optical resonator filters. Notably, certain optical resonators can be configured to exhibit high resonator quality factors to provide narrow bandwidths. A whispering gallery mode (WGM) resonator, for example, has a structure that confines light in a whispering gallery mode that is totally reflected within a closed circular optical path. Light in WGM resonators cannot exit the resonators by optical transmission and thus can be used to produce optical resonators with high optical quality factors that may be difficult to achieve with other optical resoantors such as Fabry-Perot resonators. Light in a WGM resonator “leaks” out of the exterior surface of the closed circular optical path of a WGM resonator via the evanescence field of the WG mode.